Production of titanium



' Jan. 28, 1958 I L. D. GRADY 2,821,468

PRODUCTION OF TITANIUM Filed Dec. 17. 1956 VENT Lesr D. 6

AITTORNE United States Patent PRODUCTION OF TITANIUM Lester D. Grady, Palmerton, Pa., assignor to The New Jersey Zinc Company, New York, N. Y., a corporation of New Jersey Application December 17, 1956, Serial No. 628,709

4 Claims. (Cl. 75-.5

This invention relates to the production of titanium metal and more particularly, to the recovery of the highest purity fraction of a mass of electrodeposited titanium metal.

In the electrolytic production of titanium metal, the metal is obtained as a massive deposit on the electrolytic cell cathode. Inasmuch as the electrolysis is predicated upon electrolytic decomposition of a titanium compound carried in a fused halide salt bath, the titanium deposit on the cathode contains a considerable amount of occluded salt from the bath. And when the cathode deposit is harvested by bodily withdrawing the cathode and its deposit from the fused salt bath, a further considerable quantity of salt adheres to the surface of the deposit. Accordingly, the recovery of the titanium metal component of this cathode deposit requires separation of the entrained salt from the metal, and this is usually achieved by leaching the salt away from the metal after the massive cathode deposit has been crushed to expose the entrained salt.

The lattice work of titanium metal in the cathode .deposit is composed of a dendritic mass of titanium crystals having a large range of particle sizes. The finer crystals, to the extent that their surfaces are exposed, have a larger ratio of surface area to volume than do the coarser crystals, and consequently there is more opportunity for surface oxidation per unit of volume in the case of the fine crystals than in the coarse crystals. In attempting to recover titanium metal of the highest purity from the electrolytic deposits it is natural to attempt separation of the fine, impure, high-oxygen containing particles of titanium from the higher purity, coarse material. In addition coalesced granules coarser than 8 mesh need to be broken down into their component individual crystals so that any entrained impure fines may be removed in later sizing operations. While this may appear to be a simple operation, many methods and apparatuses have been tried with little success. The difficulty is that titanium metal of high purity is soft, and milling methods that function by impact simply compress the soft metal granules without shattering them into their individual components.

Prolonged ball milling, for example, will produce flakes of metal in which very fine, highly impure, titanium particles are embedded. These embedded particles cannot be removed from the purer larger particles by subsequent screening or elutriation operations.

I have now discovered that it is possible to selectively separate the crystals of titanium in such a cathode deposit in an 'efiective manner provided that the crystalline mass is disintegrated in such way that there is substantially no welding together or coalescence of small and large crystals. I have found that the conventional procedures for disintegrating titanium metal do not achieve this result because their disintegrating action includes compressive deformation to such an extent that some fine particles are welded to the coarser particles. On the other hand, I have found that the requisite disintegration technique for practicing the invention can be achieved by use of scissor-like shearing impact.

Thus, [the method of my invention is adapted to selectively separate the relatively pure and relatively impure crystals of electrolytically deposited titanium metal from a massive cathode deposit composed essentially of a mixture of titanium crystals with adhering and entrained electrolyte salts. The method comprises first crushing the cathode deposit to form a mass of coarse aggregates not substantially smaller than that which will pass through approximately one-quarter inch screen openings, leaching the crushed mass with an aqueous medium to dissolve the electrolyte salts away from the titanium metal, and disintegrating the residual mass of titanium metal predominantly into its own component crystals with a scissor-like action between cutting blades spaced apart a distance at least as great as the maximum particle size of the individual titanium crystals in the cathode deposit. The blades move at sufficiently high speed so that the mass of titanium metal is disintegrated substantially exclusively by shearing impact, and a chemically inert atmosphere is maintained surrounding the mass of titanium metal while it is being disintegrated. The resulting disintegrated mass is classified by screening, elutriation, centrifuging or the like, to separate a relatively pure fraction composed of the relatively coarse titanium crystals from a relatively impure fraction composed of the relatively fine ltitanium crystals.

The harvested cathode deposit composed of metallic titanium and entrained electrolyte salts is first broken up by any conventional crushing operation. A jaw crusher is wholly satisfactory for this purpose, but regardless of the apparatus used in [this operation the cathode deposit should not be crushed fine enough to cause such compression of the mass as to result in a significant proportion of the fine, low-purity crystals being welded or embedded in the coarser, high-purity crystals. Thus, the crushing operation should be merely sufiicient to break up {the cathode deposit into pieces small enough to facilitate extraction of the entrained salt, the major amount of disintegration of the titanium metal into its own component crystals being effected by the scissor-like shearing impact action to which the salt-free mass is subjected pursuant to the invention. For example, a relatively low metal-content cathode deposit composed of about 35% by weight of metallic titanium and the balance entrained salt should not be crushed finer than that required for it to pass through approximately one-quarter inch screen openings. On the other hand, a relatively high metalcontent cathode deposit containing about 60% metallic titanium should not be crushed finer than that required for it to pass through approximately one inch screen openings.

The electrolyte salts are extracted by any suitable aqueous medium. For example, plain water may be used, although the use of water acidified with about 0.5% by weight of hydrogen chloride is particularly advantageous. Such a dilute hydrochloric acid solution tends to minify hydration of the salts .to relatively insoluble residues with resulting oxygen-contamination of the leached metal. It must be understood, however, that any other effective leaching medium may be used in practicing my invention, the only requirement of the leaching operation being that it produces a mass of titanium metal substantially free of entrained salts.

The resulting salt-free mass of titanium metal is then disintegrated pursuant to my invention so as to obtain the original crystals of the titanium cathode deposit substantially completely freed of one another. This disintegration is efiected by subjecting the crushed and leached mass to a scissor-like action between cutting blades spaced apart a distance at least as great as the maximum particle size of the individual titanium crystals in the leached mass. When the spacing between the blades is significantly less than the maximum crystal particle size, the larger crystals, which are relatively pure, are broken up into smaller particles within the range of the lower-purity naturally-occurring crystals.

A variety of machines presently available on the market are suitable for disintegrating the crushed and leached titanium cathode deposit pursuant to the invention. For example, the rotary cutters and knife cutters used to disintegrate plastic chips, leather and rubber scraps, asbestos, cork, paper board, and the like, are particularly suitable. These rotary cutters comprise a cylindrical enclosure provided with stationary or bed knives and an inner rotary member carrying cooperating knives. The relative motion of these knives, whose spacing may be readily adjusted, provides a scissor-like cutting action by shearing impact which is wholly different from the compressive and distorting action of roller crushers, ball mills, tumbling mills, disk grinders, and the like. In a specific rotary cutter having an outer cylindrical stator of 7 /2 inches in diameter, a rotor velocity of 1200 R. P. M. was found to be particularly satisfactory. This velocity is not critical, however; the only requirement of the rotor velocity is that it should be sufficient to effect separation of the titanium crystals by scissor-like shearing impact.

The turbulence imparted to the mass of titanium metal by its disintegration in such a rotary cutter tends to heat the metal particles and thus accelerate their oxidation if they are exposed to an oxidizing environment. Accordingly, I have found it advisable to maintain a chemically inert protective atmosphere about the titanium while it is being disintegrated. While a protective atmosphere is afforded solely by a gas such as argon, the cooling effect of water either with or without the argon is presently preferred. Thus, I have found that if the particles are simply moistened with water while being subjected to the shearing impact, the temperature of the particles is held low, but the further use of an argon atmosphere within the rotary cutter augments the protection from oxidation afforded by the Water coating on the particles. On the other hand, I have found that the use of a sufficient amount of water to completely submerge the metal particles in the rotary cutter will provide both the cooling and protection which is desirable. Still further protection of the metal against oxidation during disintegration is assured by providing the rotary cutter with charging and discharging locks which facilitate the maintenance of a non-oxidizing atmosphere within the rotary cutter.

When the titanium cathode deposit has been disintegrated pursuant to the present invention, the final product is a mass of non-oxidized individual crystals consisting of those of which the cathode deposit was composed. Of these crystals, those having a particle size range of through 8 and on 65 mesh (Tyler standard) appear to have a significantly higher degree of purity than the other larger and smaller size fractions not only with respect to their oxygen content but also with respect to the presence of nitrogen, hydrogen and the various metallic elements with which titanium is generally contaminated. Within this range, the crystals having a particle size range of through 14 and on 35 mesh have the highest purity. And for each of these ranges, the degree of ductility, measured as Brinell hardness number, is commensurate with the degree of purity.

The practice of my invention is illustrated by the following specific example:

A cathode deposit composed of 84.5 pounds of metallic titanium and 80.6 pounds of entrained electrolyte salt was removed from a cell in which titanium tetrachloride was adsorbed by a fused salt mixture initially composed of mol percent sodium chloride, 40 mol percent potassium chloride and 55 mol percent lithium chloride and further containing a small amount of lower chlorides of 5 2,821,468 a g A titanium. The cathode deposit was crushed in a jaw crusher so as to pass completely through 1 inch diameter openings. The crushed mass was then leached for two hours with aqueous hydrochloric acid containing 0.5% by weight of hydrogen chloride and maintained at a temperature of about 25 C. The leached mass was washed with water so as to obtain a coarse titanium metal substantially free of entrained salts. A sample of this material was examined microscopically and was found to contain titanium metal crystals having a maximum size of through 14 mesh (just under 1 millimeter in diameter). The resulting moist mass of titanium was then charged to the type of rotary cutter shown in the accompanying drawing in which the single figure is a front sectional elevation of the cutter. The cutter comprises an outer cylindrical frame 1. A number of bed knives 2 are mounted around the interior surface of the frame. The bed knives cooperate with rotor knives 3 carried at the extremities of arms 4 mounted on a rotatable shaft 5 axially positioned within the cylindrical frame 1. The feed material is charged through a hopper 6 at the top of the frame, and the disintegrated material which passes through a sizing screen 7 is discharged through a hopper 8. The spacing between the rotor knives 3 and the stationary bed knives 2 was one-sixteenth inch. The crushed and leached titanium metal was charged to the feed hopper 6, and the disintegrated titanium mass was discharged through the screen 7 having inch openings, thence through the discharge hopper 8. The rotor shaft 5 was rotated at a speed of 1200 R. P. M. and an atmosphere of argon was maintained within the bed casing by means of a gas inlet line 9. The 84.5 pounds of titanium were fed into the rotary cutter at the rate of 3 to 4 pounds per minute. At the end of an operating period of about 25 minutes, the discharged material had the screen and chemical analyses shown in the following table:

Oxy- Nitro- Hydro- Total Tyler Screen Weight, Brinell gen, gen, gen, Metallic Size per- Hardperperper- Impurities,

cent ness cent cent cent parts per million 4. 6 118 0.11 0. 003 0.002 about 1,000 15. 6 103 0.085 0.001 0.001 about 30 35. 2 87 0. 059 O. 001 0. 001 about 30 24. 8 102 0.077 0.001 0.001 about 40 8. 4 128 0. 14 0. 002 0.003 over 5. 0 161 0. 22 0. 003 0. 004 over 150 3. 5 189 0. 32 O. 005 0. 006 over 150 -200 +325 2. 9 215 0.43 0. 005 0.006 over 150 It can be seen from Table I that the particles having a size range of through 8 and on 65 mesh have a higher degree of purity than the largerand smaller-size fractions. The larger-size fraction was composed of aggregates of crystals which had not been completely disintegrated into their component crystals, and the smaller- -size fraction was composed of the smaller-size crystals freed from the original aggregates. Within the aforemetioned range of relatively pure crystals, the crystals having a size range of through 14 and .on 35 mesh had the highest degree of purity. The difference in purity and in Brinell hardness number are clear indications of the effectiveness of the method of the present invention.

I claim:

1. The method of selectively separating relatively pure and relatively impure crystals of electrolytically deposited titanium metal from a massive cathode deposit composed essentially of a mixture of titanium crystals with adhering and entrained electrolyte salts which comprises crushing the cathode deposit to form a mass of coarse aggregates not substantially smaller than that which will pass through approximately one-quarter inch screen openings, leaching the crushed mass with an aqueous medium to dissolve the electrolyte salts away from the titanium metal, disintegrating the residualrnass of titanium metal predominantly into its own component crystals with a scissor-like action betveen cutting blades spaced apart a distance at least as great as the maximum particle size of the individual titanium crystals and moving at sufiiciently high speed so that the mass of titanium metal is disintegrated substantially exclusively by shearing impact, maintaining a chemically inert atmosphere surrounding the mass of titanium metal while it is being disintegrated, and classifying the resulting disintegrated mass to separate a relatively pure fraction composed of the relatively coarse titanium crystals from a relatively impure fraction composed of the relatively fine titanium crystals.

2. The method of selectively separating relatively pure and relatively impure crystals of electrolytically deposited titanium metal from a massive cathode deposit composed essentially of a mixture of titanium crystals with adhering and entrained electrolyte salts which comprises crushing the cathode deposit to form a mass of coarse aggregates not substantially smaller than that which will pass through approximately one-quarter inch screen openings, leaching the crushed mass with an aqueous medium to dissolve the electrolyte salts away from the titanium metal, disintegrating the residual mass of titanium metal predominantly into its own component crystals with a scissor-like action between cutting blades spaced apart a distance at least as great as the maximum particle size of the individual titanium crystals and moving at sufficiently high speed so that the mass of titanium metal is disintegrated substantially exclusively by shearing impact, maintaining a chemically inert atmosphere surrounding the mass of titanium metal while it is being disintegrated, and classifying the resulting disintegrated mass to separate a relatively pure fraction composed of titanium particles having a size range of through 8 and on 65 mesh screen from a relatively impure fraction composed of the remaining titanium particles finer than said range.

3. The method of selectively separating relatively pure and relatively impure crystals of electrolytically deposited titanium metal from a massive cathode deposit composed essentially of a mixture of titanium crystals with adhering and entrained electrolyte salts which comprises crushing the cathode deposit to form a mass of coarse aggregates not substantially smaller than that which will pass through approximately one-quarter inch screen openings, leaching the crushed mass with an aqueous medium to dissolve the electrolyte salts away from the titanium metal, disintegrating the residual mass of titanium metal predominantly into its own component crystals with a scissor-like action between cutting blades spaced apart a distance at least as great as the maximum particle size of the individual titanium crystals and moving at sufficiently high speed so that the mass of titanium metal is disintegrated substantially exclusively by shearing impact, maintaining a chemically inert atmosphere surrounding the mass of titanium metal While it is being disintegrated, and classifying the resulting disintegrated mass to separate a relatively pure fraction composed of titanium particles having a size range of through 14 and on 35 mesh screen from a relatively impure fraction composed of the remaining titanium particles finer than said range.

4. The method of selectively separating relatively pure and relatively impure crystals of electrolytically deposited titanium metal from a massive cathode deposit composed essentially of a mixture of titanium crystals with adhering and entrained electrolyte salts which comprises crushing the cathode deposit to form a mass of coarse aggergates not substantially smaller than that which will pass through approximately one-quarter inch screen openings, leaching the crushed mass with an aqueous medium to dissolve the electrolyte salts away from the titanium metal, disintegrating the residual mass of titanium metal predominantly into its own component crystals with a scissor-like action between cutting blades spaced apart a distance at least as great as the maximum particle size of the individual titanium crystals and moving at sufliciently high speed so that the mass of titanium metal is disintegrated substantially exclusively by shearing impact, maintaining the titanium suspended in a body of Water while it is being disintegrated, and classifying the resulting disintegrated mass to separate a relatively pure fraction composed of the relatively coarse titanium crystals from a relatively impure fraction composed of the relatively fine titanium crystals.

No references cited. 

1. THE METHOD OF SELECTIVELY SEPARATING RELATIVELY PURE AND RELATIVELY IMPURE CRYSTALS OF ELECTROLYTICALLY DEPOSITED TITANIUM METAL FROM A MASSIVE CATHODE AND DEPOSIT COMPOSED ESSENTIALLY OF A MIXTURE OF TITANIUM CRYSTALS WITH ADHERING AND ENTRAINED ELECTROLYTE SALTS WHICH COMPRISES CRUSHING THE CATHODE DEPOSIT TO FORM A MASS OF COARSE AGGREGATES NOT SUBSTANTIALLY SMALLER THAN THAT WHICH WILL PASS THROUGH APPROXIMATELY ONE-QUARTER INCH SCREEN OPENINGS, LEACHING THE CRUSHED MASS WITH AN AQUEOUS MEDIUM TO DISSOLVE THE ELECTROLYTE SALTS AWAY FROM THE TITANIUM METAL, DISINTREGATING THE RESIDUAL MASS OF TITANIUM METAL PRODOMINANTLY INTO ITS OWN COMPONENT CRYSTALS WITH A SCISSOR-LIKE ACTION BETWEEN CUTTING BLADES SPACED APART A DISTANCE AT LEAST AS GREAT AS THE MAXIMUM PARTICLE SIZE OF THE INDIVIDUAL TITANIUM CRYSTALS AND MOVING AT SUFFICIENTLY HIGH SPEED SO THAT THE MASS OF TITANIUM METAL IS DISINTEGRATED SUBSTANTIALLY EXCLUSIVELY BY SHEARING IMPACT, MAINTAINING A CHEMICALLY INERT ATMOSPHERE 